1. Field of the Invention
The present invention relates to methods of forming through-tubing vent-screen tool completions in a well bore whereby gravel lost from between the tool and the well bore is prevented.
2. Description of the Prior Art
Through-tubing vent-screen completions have heretofore been utilized in well bores containing casing and perforations through the casing and cement into a producing zone. The through-tubing vent-screen tool utilized includes three basic components, i.e., a primary screen connected to a blank spacer pipe which is in turn connected to a vent-screen. The primary screen section of the tool is positioned adjacent to the perforated interval and an unconsolidated gravel pack is placed between the vent-screen and all or a portion of the blank spacer pipe. The hydrocarbons produced from the producing zone flow through the gravel pack, into the primary screen, through the blank spacer pipe and out through the vent-screen. The hydrocarbons then flow through the casing or production tubing to the surface.
The gravel, e.g., graded sand, has heretofore not been consolidated into a hard permeable mass by a hardenable resin composition coated on the gravel. The reason for this has been that the consolidated gravel pack does not have compressive forces exerted on it, and consequently, a hardenable resin composition coated on the gravel cannot consolidate the gravel. That is, because the gravel particles are not packed together under compressive forces, the particles in the pack do not contact each other with sufficient force for the pack to be consolidated into a hard permeable pack.
The function of the gravel pack is to prevent formation sand and fines from flowing out of the producing zone with produced hydrocarbons. Heretofore, the unconsolidated gravel has been placed in the well bore around the vent-screen and around the blank spacer pipe whereby the gravel pack has sufficient height to maintain the stability of the gravel pack while the well is producing hydrocarbons. The gravel pack around the blank spacer pipe prevents formation sand and fines from flowing out of the producing zone with produced hydrocarbons. However, if the blank spacer pipe and the height of the gravel pack are too short, the gravel pack will become unstable as the gravel fluidizes whereby a portion of the hydrocarbons flow through the gravel pack and formation sand and fines are produced with the hydrocarbons. More often, the produced hydrocarbons by-pass the through-tubing vent-screen tool, fluidizing the gravel and carrying it and formation sand and fines to the surface.
There is often a limited space between the primary screen and the top vent-screen in the well bore. As a result, it would be desirable to be able to utilize a short blank pipe and gravel pack that separate the two screens.
While sticky tackifying agents have heretofore been coated on the gravel for the purpose of increasing the cohesiveness between the gravel particles and thus increasing the gravel pack resistance to fluidization, the gravel pack has still become fluidized when it is exposed to high production flow rates whereby it flows out of the well bore with produced fluids and formation sand and fines are carried to the surface.
Thus, there are needs for an improved through-tubing vent-screen completion whereby the gravel pack is consolidated into a hard permeable pack which is short, will not fluidize and is capable of continuously preventing the production of formation sand and fines with produced hydrocarbons.